Power converter

ABSTRACT

A power converter is provided for direct conversion of multi-phase AC power to AC power. The power converter includes a conversion circuit and a plurality of output lines. The conversion circuit has first and second switching elements that are configured to be connected to phases of the multi-phase AC power for bidirectional switching of energizing current. The output lines are connected to the conversion circuit. The first and second switching elements have output terminals. The output terminals of the first and second switching elements are arranged in first and second rows. The output terminals of the first and second switching elements face each other. The first output lines include two first output lines including first and second widely shaped bus bars connected to the output terminals of the first and second switching elements, respectively. The first output lines extending out in one direction, and line up in an upright direction.

TECHNOLOGICAL FIELD

The present invention relates to a power converter for direct conversionof AC power to a desired AC power frequency.

BACKGROUND TECHNOLOGY

A matrix converter is one known power converter in which the partsconstituting the device are few in number, making possible a smallerdevice; and which is able to convert AC power directly and efficientlyinto AC power (Patent Document 1)

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: Japanese Laid-Open Patent Application 2006-333590

DISCLOSURE OF THE INVENTION Problems to Be Solved by the Invention

However, a problem with the aforedescribed matrix converter of the priorart is that because the multiple IGBT are arranged in series, and theoutput lines from the IGBT are connected in consolidated fashion, theoutput lines are long. Particularly in a power converter in whichhigh-frequency current must flow through the output lines, longer wirelengths result in susceptibility to the effects of the L component.

An object of the present invention is to provide a power converterwhereby the output lines can be shorter.

Means Used to Solve the Above-Mentioned Problems

The present invention solves the above-mentioned problem through aplurality of switching means constituting a power conversion circuit, inwhich bus bars of wide shape are arranged lining up in an uprightdirection such that the output lines lead out in one direction.

Effect of the Invention

According to the present invention, a plurality of switching means arearranged lining up, whereby the output lines can be lead out in onedirection, and the output lines can be made shorter.

[BRIEF DESCRIPTION OF THE DRAWINGS]

FIG. 1

An electrical circuit diagram showing a power conversion system to whichan embodiment of the present invention is applied.

FIG. 2

A plan view, left/right side views, front view, and back view showingthe power converter according to an embodiment of the present invention.

FIG. 3

A plan view of the layout of IGBT, filter capacitors, and bus bars inthe power converter of FIG. 2.

FIG. 4

A plan view, side view, front view, and back view showing a portion ofthe power converter of FIG. 2.

FIG. 5

A plan view and front view showing in simplified form a portion of thepower converter of FIG. 2.

PREFERRED EMBODIMENTS OF THE INVENTION

(Overview of Power Conversion System 1)

An overview of a power conversion system to which an embodiment of thepresent invention is applied shall be described first, making referenceto FIG. 1. The power conversion system 1 of the present example is asystem in which three-phase AC power supplied by a three-phase AC powersupply 2 is directly converted to single-phase AC power by a powerconverter 3 according to an embodiment of the present invention, whichpower is then stepped up or stepped down, as appropriate, by atransformer 4, and converted to DC voltage by a rectifier 5, for use incharging a secondary cell 6. 7 denotes a smoothing circuit.

In the power conversion system 1 of the present example, the phases(shown as phase R, phase S, and phase T) of the output lines whichsupply three-phase AC power from the three-phase AC power supply 2 areprovided with a filter circuit 8 for attenuation of harmonics, as acountermeasure against noise. The filter circuit 8 of the presentexample is provided with three filter reactors 81 connected to thephases R, S, and T, and with six filter capacitors 82L, 82R connectedbetween the phases R, S, and T. The layout of the filter capacitors 82L,82R (shown by filter capacitors 821-836 in FIGS. 2 and 4) shall bediscussed later.

In the power conversion system 1 of the present example, three-phase ACpower is supplied to the power converter 3 through the filter circuit 8,and converted to single-phase AC power. The power converter 3 of thepresent example is provided with six bidirectional switching elements 31(311-316) arrayed in a matrix, in corresponding fashion to phase R,phase S, and phase T. In the following description, symbol 31 shall beemployed when referring generically to any one bidirectional switchingelement, whereas [symbols] 311-316 shall be employed when referring tospecific elements among the six bidirectional switching elements asshown in FIG. 1.

Each of the bidirectional switching elements 31 in the present exampleis respectively constituted by an IGBT module in which an IGBT (a typeof semiconductor switching element) is combined with a freewheelingdiode in an anti-parallel connection. The constitution of a singlebidirectional switching element is not limited to that illustrated here,and a different constitution, for example, one involving ananti-parallel connection of two reverse blocking IGBT elements, wouldalso be acceptable.

In order to protect the bidirectional switching elements 31 from surgevoltage generated in association with ON/OFF operation of thebidirectional switching elements 31, the bidirectional switchingelements 31 are respectively provided with snubber circuits 32 (321-326)which are a combination of three diodes and one snubber capacitor 327(see the circuit diagram at lower right in the drawing) at the inputside and the output side of the bidirectional switching element 31. Inthe following description, symbol 32 shall be employed when referringgenerically to any single snubber circuit, whereas [symbols] 321-326shall be employed when referring to specific snubber circuits among thesix snubber circuits as shown in FIG. 1.

The power conversion system 1 of the present example is provided with amatrix converter control circuit 9 for respective ON/OFF control of thebidirectional switching elements 31 of the power converter 3. The matrixconverter control circuit 9 inputs the voltage value supplied by thethree-phase AC power supply 2, the currently output DC current value,and a target current command value, and on the basis thereof, controlsthe respective gate signals of the bidirectional switching elements 31,and adjusts the single-phase AC power output to the transformer 4, tothereby obtain DC power that matches the target.

The voltage of the single-phase AC power converted by the powerconverter 3 is stepped up or stepped down to a predetermined voltage bythe transformer 4. The rectifier 5 is provided with four rectifierdiodes 51-54, and converts voltage-regulated single-phase AC power to DCpower. The smoothing circuit 7 is provided with a coil 71 and acapacitor 72, and smooths pulsating current included in rectified DCcurrent, to produce a condition that more closely approximates DC.

In the power conversion system 1 of the present example constituted inthe above manner, three-phase AC power supplied by the three-phase ACpower supply 2 is directly converted to single-phase AC power by thepower converter 3, and after regulation to appropriate voltage, isconverted to DC power. The secondary cell 6 is charged thereby. Thepower conversion system 1 discussed above is merely one example ofapplication of the power converter 3 according to the present invention,and the present invention is not limited to application in the powerconversion system in question. Specifically, application in other powerconversion systems is possible as well, provided that at least the powerbeing converted and/or the converted power is multi-phase AC power.

(Arrangement of Components in Power Converter 3)

Next, the constitution of arrangement of the components that constitutethe power converter 3 shall be described, making reference to FIGS. 2 to5. Components assigned the same symbols as in FIG. 1 indicate thosehaving mutually corresponding relationships. In FIGS. 2 and 3, therectifier 5 and the smoothing circuit 7 are shown besides the powerconverter 3 of the present example, but the transformer 4 of FIG. 1 liesoutside of the drawing.

FIG. 3 is a plan view showing a mid-assembly state in which the sixbidirectional switching elements 31 (any one of which is also referredto as an IGBT module) have been mounted on the upper surface of a heatsink 10, and bus bars for connecting the terminals of the bidirectionalswitching elements 31 have been mounted thereon. FIG. 2 is a plan view,left/right side views, front view, and back view showing the assembledstate in which the three diodes constituting the snubber circuits 32 andthe six filter capacitors 82 of the filter circuit 8 have been mountedthereon. The components constituting the power converter 3 of thepresent example overlap one another in plan view, and therefore in thefollowing description, relevant portions are in some instances shown inseparate drawings (FIG. 4, 5) to which reference shall be made as well.

As shown in FIGS. 3 and 5, the bidirectional switching elements 31 ofthe present example are provided, on the upper surface of the modulepackage, with an input terminal of the bidirectional switching element31, output terminal, and two IGBT midpoint terminals constituting apair. Of the six bidirectional switching elements 311-316 shown in FIGS.3 and 5, the terminals at the left ends of the three bidirectionalswitching elements 311, 313, 315 on the left side are input terminals(in FIG. 3 these are hidden by the bus bars 333, 334, 335), theterminals at the right ends are output terminals, and the centerterminals are midpoint terminals. Of the six bidirectional switchingelements 311-316 shown in FIGS. 3 and 5, the terminals at the right endsof the three bidirectional switching elements 312, 314, 316 on the rightside are input terminals (in FIG. 3 these are hidden by the bus bars333, 334, 335), the terminals at the left ends are output terminals, andthe center terminals are midpoint terminals. The gate terminals of thebidirectional switching elements 31 are provided to another section ofthe module package.

As shown in FIGS. 2, 3, and 5, the six bidirectional switching elements311-316 are fastened to the upper surface of the heat sink 10 byfastening means such as bolts or the like. As shown in the drawings,these six bidirectional switching elements 311-316 are respectivelyarranged lining up to the left and right of a center line CL, in pairsconstituted by the bidirectional switching elements 311 and 312, thebidirectional switching elements 313 and 314, and the bidirectionalswitching elements 315 and 316. In other words, the pairs of the twobidirectional switching elements 311 and 312, the bidirectionalswitching elements 313 and 314, and the bidirectional switching elements315 and 316 are respectively arranged lining up to the left and rightfrom the center line CL, along the direction of extension of the threeterminals (the input terminal, midpoint terminal, and output terminal)of a single bidirectional switching element 31. Herein, this array isalso referred to as “arrangement in rows with respect to the center lineCL or to output lines P, N connecting the output terminals.” Abidirectional switching element pair refers to a pair of bidirectionalswitching elements connected to the same phase R, S, or T input line.

By arranging the pairs constituted by the bidirectional switchingelements 311 and 312, the bidirectional switching elements 313 and 314,and the bidirectional switching elements 315 and 316 so as to line up tothe left and right of the center line CL in this manner, the layout isone in which the output lines P, N (bus bars 331 a, 332 a) can be ledout to minimum length in one direction. Because output of high-frequencyAC power over longer wire lengths entails greater susceptibility to theeffect of the L component, the effect of the L component can beminimized through the arrangement in the present example. Specifically,the output lines P, N will include the output lines that approximatestraight lines, at least up to the transformer 4.

As mentioned above, the terminals at the right ends of the bidirectionalswitching elements 311, 313, 315 to the left side of the center line CLare all output terminals, while the terminals at the left ends are allinput terminals. Conversely, the terminals at the left ends of thebidirectional switching elements 312, 313, 316 to the right side of thecenter line CL are all output terminals, while the terminals at theright ends are all input terminals.

The bus bars 333, 334, 335 the input lines R, S, T of the three-phase ACpower supply 2 lead towards the center line CL and connect to the inputterminals at the left ends of the bidirectional switching elements 311,313, 315 to the left side of the center line CL, whereas the input linesR, S, T constituted by further extension of these bus bars 333, 334, 335are connected to the input terminals at the right ends of thebidirectional switching elements 312, 314, 316 to the right side of thecenter line CL. Specifically, phase R is connected to the inputterminals of the bidirectional switching elements 311, 312, phase S isconnected to the input terminals of the bidirectional switching elements313, 314, and phase T is connected to the input terminals of thebidirectional switching elements 315, 316, respectively. The bus bars333, 334, 335 constituting the input lines R, S, T lead in one directionfrom either left or right, and are then extended to the right or left inthe other direction, whereby the distance in the left-right direction ofthe heat sink 10 can be shorter, and the filter capacitors 82L, 82R(discussed later) can be arranged uniformly, contributing to a simplerlayout and conserving space.

The bus bar 333 constituting the input line R is connected between theinput terminals of the bidirectional switching elements 311 and 312constituting a pair arranged to left and right of the center line CL,the bus bar 334 constituting the input line S is connected between theinput terminals of the bidirectional switching elements 313 and 314, andthe bus bar 335 constituting the input line T is connected between theinput terminals of the bidirectional switching elements 315 and 316. Thewires corresponding to these bus bars 333, 334, 335 are shown by likesymbols in the equivalent circuit of FIG. 1 as well. The connectionstructure afforded by these bus bars 333-335 is not essential in termsof the functionality of the power converter 3.

The pairs constituted by the bidirectional switching elements 311 and312, the bidirectional switching elements 313 and 314, and thebidirectional switching elements 325 and 316 arranged to left and rightfrom the center line CL are respectively connected by these bus bars333, 334, 335, whereby the filter capacitors 82L, 82R provided betweenphases can be mutually shared. Specifically, a filter capacitor 821 isprovided between phase R and phase S at the left side in the drawing,and a filter capacitor 824 is provided between phase R and phase S atthe right side, the input terminals of the bidirectional switchingelements 311, 312 to which phase R is input being connected by the busbar 333. Consequently, noise from phase R of the three-phase AC powersupply 2 is filtered through cooperation by the two filter capacitors821, 824, whereby a single filter capacitor can be smaller in capacity,as a result of which the filter capacitor can be smaller in size. Thesame is true for phase S and phase T as well.

These bus bars 333-335 and the bus bars 331, 332 constituting the outputlines P, N intersect in plan view, but as shown in front view in FIGS. 2and 5, the bus bars 331, 332 of the output lines P, N are established atlocations higher than the bus bars 333-335 which interconnect the inputterminals, thereby providing a constitution that avoids interferenceresulting from three-dimensional intersection.

In FIG. 1, the input lines R, S, T leading from the three-phase AC powersupply 2 to the power converter 3 are constituted so as to branchbetween the filter reactor 81 and the filter capacitors 82L, 82R, butmay instead branch to the upstream side from the filter reactor 81,furnishing the filter reactor 81 respectively to the branched inputlines R, S, T.

The single bus bar 331 a constituting the output line P of the powerconverter 3 is connected to the output terminals at the right ends ofthe bidirectional switching elements 311, 313, 315 to the left side fromthe center line CL, whereas the single bus bar 332 a constituting theoutput line N of the power converter 3 is connected to the outputterminals at the left ends of the bidirectional switching elements 312,314, 316 to the right side from the center line CL. These bus bars 331a, 332 a are connected at the distal end side to the transformer 4. Thefollowing bus bars, including these bus bars 331 a, 332 a, areconstituted by conductors of excellent conductivity, such as copper orthe like.

The pair of bus bars 331 a, 332 a constituting the output lines P, N ofthe power converter 3 are relatively wider in shape than bus bars 331 b,332 b discussed below, and as shown in plan view and front view in FIG.2, are arranged lining up upright with respect to a principal surface ofthe heat sink 10. The width dimensions of these bus bars 331 a, 332 aare selected according to the rated current; wider shape allows forgreater current flow, due to the skin effect observed with ahigh-frequency current. Moreover, by adopting a wider shape and anupright arrangement, the distance between the left-side bidirectionalswitching elements 311, 313, 315 and the right-side bidirectionalswitching elements 312, 314, 316 can be shorter, and the power converter3 can be smaller in the left-right direction.

In contrast to this, the pair of bus bars 331 b, 332 b constituting theoutput lines P, N of the power converter 3 are connected and fastened tothe distal ends of the bus bars 331 a, 332 a, and arranged lining up ina horizontal direction with respect to a principal surface of the heatsink 10 as shown in plan view and front view in FIG. 2. While these busbars 331 b, 332 b are relatively narrower in width than the bus bars 331a, 332 a, as shown in front view in FIG. 2, each single bus bar 331 b,332 b respectively includes multiple (in the present example, two) busbars arranged stacked at predetermined spacing. Due to the relativelynarrower width with respect to the 331 a, 332 a, if constituted by asingle bus bar, the current density of high-frequency current would begreater due to the skin effect; however, by virtue of being constitutedof a plurality of bus bars, high-frequency current flow comparable tothat of the bus bars 331 b, 332 b can be achieved. By arranging the busbars 331 b, 332 b to line up in a horizontal direction, the right-endconnection terminals to the transformer 4 can be arrayed in the sameorientation, as shown in plan view in FIG. 2.

In the present example, the filter circuit 8 includes the six filtercapacitors 821-826 respectively arranged in sets of three on the inputlines, to the left side and the right side of the center line CL asshown in FIGS. 2, 4, and 5. The filter capacitor 821 on the left side isprovided between phase R and phase S corresponding to the input terminalof the bidirectional switching element 311. Likewise, the filtercapacitor 822 on the left side is provided between phase S and phase Tcorresponding to the input terminal of the bidirectional switchingelement 313, and the filter capacitor 823 on the left side is providedbetween phase T and phase R corresponding to the input terminal of thebidirectional switching element 315. The filter capacitor 824 on theright side is provided between phase R and phase S corresponding to theinput terminal of the bidirectional switching element 312, the filtercapacitor 825 on the right side is provided between phase S and phase Tcorresponding to the input terminal of the bidirectional switchingelement 314, and the filter capacitor 826 on the right side is providedbetween phase T and phase R corresponding to the input terminal of thebidirectional switching element 316.

By arranging the six filter capacitors 821-826 in sets of three to theleft and right of the center line CL in respectively correspondingfashion to the six bidirectional switching elements 311-316 which havebeen arranged in sets of three each to the left and right of the centerline CL in this manner, the distances over which the respectiveconnecting wires of the filter capacitors 821-826 and the bidirectionalswitching elements 311-316 are routed can be shorter.

In the present example, the filter capacitors 821-826 in sets of threerespectively situated at left and right are arranged to the outside,with respect to the center line CL, from the area in which the sixbidirectional switching elements 311-316 are provided. In specificterms, as shown in FIGS. 2, 4, and 5, the elements are fastened to theupper part of the bus bars 333, 334, 335. By arranging the filtercapacitors 821-826 further to the outside from the bidirectionalswitching elements 311-316, the spacing in the left-right directionbetween the left and right bidirectional switching elements 311-316 canbe shortest, the span of the heat sink 10 in the left-right directioncan be set to the shortest span, and as a result the heat sink 10 can bemore compact, as compared with the case in which the six filtercapacitors are arrayed at the center.

Next, the mounted condition of the filter capacitors 821-826 provided insets of three respectively to the left and right of the center line CLwill be described on the basis of the plan views and side views of theactual device shown in FIGS. 2 to 4.

Before doing so, the connection configuration of the bus bars shall bedescribed again. As shown in FIG. 3, the bus bar 331 a connects theoutput terminals of the bidirectional switching elements 311, 313, 315,and serves as the output line P leading to the transformer 4 through thebus bar 331 b. The bus bar 332 a connects the output terminals of thebidirectional switching elements 312, 314, 316, and serves as the outputline N leading to the transformer 4 through the bus bar 332 b.

The bus bar 333 is a bus bar to which the phase R input line isconnected and which connects the input terminals of the bidirectionalswitching elements 311 and 312, and extends [to areas] to the outside toleft and right from both input terminals, in which [areas] the filtercapacitors 821, 823, 824, 826 are connected directly. Likewise, the busbar 334 is a bus bar to which the phase S input line is connected andwhich connects the input terminals of the bidirectional switchingelements 313 and 314, and extends [to areas] to the outside to left andright from both input terminals, in which [areas] the filter capacitors821, 822, 824, 825 are connected directly. The bus bar 335 is a bus barto which the phase T input line is connected and which connects theinput terminals of the bidirectional switching elements 315 and 316, andextends [to areas] to the outside to left and right from both inputterminals, in which [areas] the filter capacitors 822, 823, 825, 826 areconnected directly. Because the filter capacitors 821-826 directlyconnect to the bus bars 333-335 in this way, the connection structure issimpler.

As shown in FIGS. 2, 4, and 5, the filter capacitors 82L-82L, in sets ofthree respectively arranged at left and right, are arranged to theoutside with respect to the center line CL, and moreover are arrangedsuch that the centers of the filter capacitors 821, 822, 823 arepositioned at the apices of a triangle (more preferably an isoscelestriangle or an equilateral triangle) one apex of which faces towards anoutward direction. By arranging the three filter capacitors 82L, 82R onthe apices of a triangle, the wire lengths among the capacitors can beset to the shortest distance, the power converter 3 can be made morecompact, and the capacitors can be tuned to one another. Moreover, byarranging one apex to face towards an outward direction, the balanceamong the wires connecting the capacitors can be improved, and thedistances to the bus bars 333, 334, 335, can be shorter, as compared toan array in which one apex faces towards an inward direction.Furthermore, by arranging the filter capacitors 821-826 on the uppersurfaces of the bus bars, in other words, arranging the filtercapacitors 821-826 on the opposite side of the bus bars from thebidirectional switching elements 311-316, the degree of freedom indesign of the layout of the filter capacitors 821-826 is greater.

Next, an example of mounting the three diodes and the one snubbercapacitor 327 constituting the snubber circuit 32 shown in FIG. 1 willbe described. As shown in FIG. 1, in the snubber circuit 321 of thebidirectional switching element 311 for example, one terminal isconnected to the input terminal of the bidirectional switching element311, another terminal is connected to the midpoint terminal of thebidirectional switching element, and yet another terminal is connectedto the output terminal of the bidirectional switching element 311,respectively. Therefore, as shown in FIG. 2, the three diodes arerespectively fastened and connected to brackets 351-356 comprisingconductors which are connected to the midpoint terminals of thebidirectional switching elements 31L, 31R.

In the present example, a relatively large electrolytic capacitor isused for the snubber capacitor 327, and the snubber capacitor 327 isshared by the six snubber circuits 321-326 (see FIG. 2). The snubbercapacitor 327 and the three diodes are connected by wires.

The embodiment shown above has the following effects.

1) According to the present example, the six filter capacitors 821-826,in sets of three to the left and right of the center line CL, arearranged in respectively corresponding fashion to the six bidirectionalswitching elements 311-316 which have been arranged in sets of three tothe left and right of the center line CL, whereby the distances overwhich the respective connecting wires of the filter capacitors 821-826and the bidirectional switching elements 311-316 are routed can beshorter.

2) In the present example, the pairs of the bidirectional switchingelements 311 and 312, the bidirectional switching elements 313 and 314,and the bidirectional switching elements 315 and 316 are respectivelyarranged lining up to the left and right of the center line CL, wherebythe layout is such that the output lines P, N (the bus bars 331 a, 332a) can be lead out a short [distance] in one direction. Consequently,while output of high-frequency AC power over longer wire lengths entailsgreater susceptibility to the effect of the L component, the effect ofthe L component can be minimized through the arrangement in the presentexample.

3) In the present example, the pair of bus bars 331 a, 332 aconstituting the output lines P, N are relatively wider in shape thanthe bus bars 331 b, 332 b, and are arranged lining up upright withrespect to a principal surface of the heat sink 10. The wider shapeallows for greater current flow, due to the skin effect observed with ahigh-frequency current. Moreover, by adopting a wider shape and anupright arrangement, the distance between the left-side bidirectionalswitching elements 311, 313, 315 and the right-side bidirectionalswitching elements 312, 314, 316 can be shorter, and the power converter3 can be smaller in the left-right direction.

4) In the present example, the bus bars 331 b, 332 b constituting theoutput lines P, N are narrower in width relative to the bus bars 331 a,332 a, and a single bus bar includes multiple bus bars stacked atpredetermined spacing, and furthermore arranged lining up in ahorizontal direction with respect to a principal surface of the heatsink 10. Due to the narrower width of the bus bars 331 b, 332 b relativeto the bus bars 331 a, 332 a, monopolization of space is kept to aminimum, and because the bus bars can be lined up in a horizontaldirection, the connection terminals to the transformer 4 can be arrayedin the same orientation. Moreover, because a single bus bar includesmultiple bus bars stacked at predetermined spacing, high-frequencycurrent flow comparable to that through the bus bars 331 a, 332 a can beachieved due to the skin effect.

5) In the present example, the filter capacitors 821-826 in sets ofthree respectively situated at left and right are arranged to theoutside, with respect to the center line CL, from the area in which thesix bidirectional switching elements 311-316 are provided, whereby thespacing in the left-right direction between the left and rightbidirectional switching elements 31L, 31R can be shortest. Consequently,the span of the heat sink 10 in the left-right direction can be set tothe shortest span, and as a result the heat sink 10 can be more compact.

6) In the present example, the bus bars 333, 334 constituting the inputlines lead in one direction from either left or right, and extend toright or left in the other direction, thereby respectively connectingthe input terminals of the pairs of the bidirectional switching elements311 and 312, of the bidirectional switching elements 313 and 314, and ofthe bidirectional switching elements 325 and 316 which are arranged toleft and right of the center line CL. In so doing, the span of the heatsink 10 in the left-right direction can be shorter, and the filtercapacitors 82L, 82R (discussed later) can be arranged uniformly,contributing to a simpler layout and conserving space. Moreover, thefilter capacitors 82L, 82R provided between phases can be mutuallyshared, whereby a single filter capacitor can be smaller in capacity, asa result of which the filter capacitor can be smaller in size.

7) In the present example, the filter capacitors 821-826 are arranged onthe upper surfaces of the bus bars 333, 334, 335, in other words, thefilter capacitors 821-826 are arranged on the opposite side of the busbars from the bidirectional switching elements 311-316, therebyaffording a greater degree of freedom in design of the layout of thefilter capacitors 821-826.

8) In the present example, the three filter capacitors 821, 822, 823 arearranged on the apices of a triangle, whereby the wire lengths among thecapacitors can be set to the shortest distance, the power converter 3can be made more compact, and the capacitors can be tuned to oneanother.

9) In the present example, the three filter capacitors arranged atriangle are arranged such that one apex faces towards an outwarddirection, whereby the balance among the wires connecting the capacitorscan be improved, and the distances to the bus bars 333, 334, 335, can beshorter, as compared to an array in which one apex faces towards aninward direction.

Additional Embodiments

The present invention can be modified, as appropriate, to embodimentsother than the preceding. While modifications of the present inventionare described below, the present invention should not be construed asbeing limited to the preceding embodiment or to the embodimentshereinbelow.

In the preceding embodiment, the filter capacitors 82L, 82R, in sets ofthree respectively to the left and right, are arranged to the outside,with respect to the center line CL, from the bidirectional switchingelements 311, 313, 315 and 312, 314, 316, but could instead be arrangedbetween the bidirectional switching elements 311, 313, 315 and 312, 314,316 which are arrayed to left and right with respect to the center lineCL.

In the preceding embodiment, of the six bidirectional switching elements311-316, the bidirectional switching elements 311, 313, 315 are arrangedto the left side, and the bidirectional switching elements and 312, 314,316 are arranged to the right side, with respect to the center line CL.However, it would be acceptable to arrange the bidirectional switchingelements 311, 313, 315 and the bidirectional switching elements and 312,314, 316 along the center line CL.

In the preceding embodiment, of the six bidirectional switching elements311-316, the bidirectional switching elements 311, 313, 315 are arrangedto the left side, and the bidirectional switching elements and 312, 314,316 arranged to the right side, with respect to the center line CL,while furnishing the input terminals and the output terminals of thebidirectional switching elements in line-symmetric fashion side withrespect to the center line CL. However, it would be acceptable also toarrange the bidirectional switching elements 311, 313, 315 to the leftside, and arrange the bidirectional switching elements 312, 314, 316 tothe right side, with respect to the center line CL, while adoptingidentical arrangements for the input terminals and the output terminalsof the bidirectional switching elements.

In the preceding embodiment, the filter capacitors 821-826 are providedbetween phases, doing so such that each single one correspondsrespectively to one of the six bidirectional switching elements 311-316.However, the filter capacitors 821-826 could instead be provided betweenphases, doing so in such a way that several correspond respectively toone of the six bidirectional switching elements 311-316. In this case,the filter capacitors may be arranged at the center of the powerconverter 3, or outside the power converter 3. When arranged at thecenter of the power converter 3, empty space can be utilized, wherebythe size of the power converter 3 can be minimized to the greatestpossible extent.

The aforementioned bidirectional switching elements 311, 313, 315correspond to the first switching means according to the presentinvention; the aforementioned bidirectional switching elements 312, 314,316 correspond to the second switching means according to the presentinvention; the aforementioned power converter 3 corresponds to theconversion circuit according to the present invention; theaforementioned bus bars 331 a, 332 a correspond to the first outputlines according to the present invention; and the aforementioned busbars 331 b, 332 b correspond to the second output lines according to thepresent invention.

KEY TO SYMBOLS

1: power conversion system

2: three-phase AC power supply

3: power converter

-   -   31, 311-316: bidirectional switching elements    -   32, 321-326: snubber circuits    -   327: snubber capacitor    -   341-348: bus bars    -   351-356: brackets

4: transformer

5: rectifier

6: secondary cell

7: smoothing circuit

8: filter circuit

-   -   81: filter reactor    -   82L, 82R, 821-826, 831-836: filter capacitors

9: matrix converter control circuit

10: heat sink

1. A power converter for direct conversion of multi-phase AC power to ACpower, the power converter comprising: a conversion circuit having aplurality of first switching elements configured to be connected tophases of the multi-phase AC power for bidirectional switching ofenergizing current, and a plurality of second switching elementsconfigured to be connected to the phases of the multi-phase AC power,for bidirectional switching of energizing current; and a plurality ofoutput lines connected to the conversion circuit; the first switchingelements having output terminals and the second switching elementshaving output terminals, the output terminals of the first switchingelements being arranged in a first row, the output terminals of thesecond switching elements being arranged in a second row and facing theoutput terminals of the first switching elements, the output linesincluding a pair of first output lines including a first widely shapedbus bar connected to the output terminals of the first switchingelements and a second widely shaped bus bar connected to the outputterminals of the second switching elements, the first output linesextending out in one direction, and lining up in an upright direction.2. The power converter according to claim 1, wherein the output linesinclude a pair of second output lines that are connected to distal endsof the first output lines, respectively, the second output lines beingnarrower in width than the first output lines, and arranged in ahorizontal direction; each of the second output lines has a plurality ofoutput lines being stacked at predetermined spacing in each of thesecond output lines.
 3. The power converter according to claim 1,further comprising a plurality of input lines connected to a respectiveone of input terminals of the first switching elements and the secondswitching elements; and the output lines being connected to outputterminals provided to an inside from the input terminals.
 4. The powerconverter according to claim 3, wherein the output lines are arranged toan upper side from the input lines in a vertical direction.
 5. The powerconverter according to claim 1, further comprising a plurality ofcapacitors connected to the conversion circuit, the capacitors beingarranged to an outside with respect to the first and second rows of thefirst and second switching elements.
 6. The power converter according toclaim 5, wherein the capacitors connected to the first switchingelements and the capacitors connected to the second switching elementsare electrically connected.
 7. The power converter according to claim 3,wherein paired ones of the input terminals are arranged in a row in thefirst switching elements and the second switching elements, and theinput lines extend in a direction in which the paired ones of the inputterminals are lined up, and extend from one of the input terminals toanother of the input terminals of the paired input terminals.
 8. Thepower converter according to claim 2, further comprising a plurality ofinput lines connected to a respective one of input terminals of thefirst switching elements and the second switching elements; and theoutput lines being connected to output terminals provided to an insidefrom the input terminals.
 9. The power converter according to claim 8,wherein the output lines are arranged to an upper side from the inputlines in a vertical direction.
 10. The power converter according to anyof claim 2, further comprising a plurality of capacitors connected tothe conversion circuit, the capacitors being arranged to an outside withrespect to the first and second rows of the first and second switchingelements.
 11. The power converter according to claim 10, wherein thecapacitors connected to the first switching elements and the capacitorsconnected to the second switching elements are electrically connected.12. The power converter according to claim 4, wherein paired ones of theinput terminals are arranged in a row in the first switching elementsand the second switching elements, and the input lines extend in adirection in which the paired ones of the input terminals are lined up,and extend from one of the input terminals to another of the inputterminals of the paired input terminals.
 13. The power converteraccording to claim 3, further comprising a plurality of capacitorsconnected to the conversion circuit, the capacitors being arranged to anoutside with respect to the first and second rows of the first andsecond switching elements.
 14. The power converter according to claim13, wherein the capacitors connected to the first switching elements andthe capacitors connected to the second switching elements areelectrically connected.
 15. The power converter according to claim 4,further comprising a plurality of capacitors connected to the conversioncircuit, the capacitors being arranged to an outside with respect to thefirst and second rows of the first and second switching elements. 16.The power converter according to claim 15, wherein the capacitorsconnected to the first switching elements and the capacitors connectedto the second switching elements are electrically connected.
 17. Thepower converter according to claim 4, wherein paired ones of the inputterminals are arranged in a row in the first switching elements and thesecond switching elements, and the input lines extend in a direction inwhich the paired ones of the input terminals are lined up, and extendfrom one of the input terminals to another of the input terminals of thepaired input terminals.
 18. The power converter according to claim 5,wherein paired ones of the input terminals are arranged in a row in thefirst switching elements and the second switching elements, and theinput lines extend in a direction in which the paired ones of the inputterminals are lined up, and extend from one of the input terminals toanother of the input terminals of the paired input terminals.
 19. Thepower converter according to claim 6, wherein paired ones of the inputterminals are arranged in a row in the first switching elements and thesecond switching elements, and the input lines extend in a direction inwhich the paired ones of the input terminals are lined up, and extendfrom one of the input terminals to another of the input terminals of thepaired input terminals.